OA equipment including electrophotographic apparatus and electrostatic recording apparatus such as copiers, facsimile equipment, printers are constituted of various parts, and blades, rollers and belts are essential parts playing such a roll as charging, developing, transfer, fixation, static electricity elimination, cleaning, paper feeding or transportation in electrophotographic processes. These parts are mostly made of polyurethane materials and, in many cases, they must be provided with a conductivity of about 104 to 1012 Ω·cm from the functional viewpoint.
The most popular measures that has so far been taken for providing polyurethane members for OA equipment parts with conductivity comprises molding a polyurethane material prepared by kneading and dispersing carbon black with and in the polyol constituent, for instance.
However, it is very difficult to provide such moldings wholly and uniformly with stable conductivity by the method comprising dispersing, by kneading, of carbon black, since a slight deviation in the amount of addition of such a substance, slight changes in such conditions as material temperature, molding temperature and molding time and, further, the use of a different molding method result in changes in conductive path morphology, hence in great variations in conductivity, in particular in the volume resistivity range of 106 to 1011 Ω·cm.
Furthermore, carbon black is generally higher in specific gravity than polyurethanes, so that it settles and is distributed unevenly during molding and, further according to the moldings morphology, leading to development of faults in conductive paths of carbon black and making it difficult to stably provide the moldings with uniform conductivity. This tendency is strong especially with the moldings molded by the centrifugal molding method in which a great centrifugal force is exerted on the materials. Therefore, to cope with such difficulties, it is indispensable to strictly control the manufacturing conditions according to the moldings morphology and/or molding method. Moreover, with the conductive polyurethanes obtained by such methods, the electric resistance is highly dependent on the voltage applied, hindering the development of high-performance electrophotographic apparatus and electrostatic recording apparatus.